A number of wood species is highly

A number of wood species is highly valued for the ability of their
heartwood to naturally resist biodegradation; these include
redwood, cedars, teak, and many tropical hardwoods. The durability
of these species generally relates to the presence of fungitoxic
extractives in the heartwood, although enhanced water resistance
and the presence of mineral deposits can also impart resistance
against specific agents of decay (Scheffer and Cowling, 1966; Hillis,
1987). The reputations of these species for durability were largely
developed through experiences with lumber derived from oldgrowth
trees. As the forest products industry has transitioned
from using old-growth resources to more heavily managed forests,
changes have been observed in durability. In some cases, the
changes are due to a higher proportion of non-durable sapwood,
but a number of studies has shown that heartwood from secondgrowth
teak and redwood may be less durable (Clark and
Scheffer, 1983; Mockus-Lubin et al., 1986; Nault, 1988; Freitag
and Morrell, 2001; Haupt et al., 2003). It has also long been